The present invention relates to a prosthesis, and, in particular, to a shoulder prosthesis including a humeral stem. The present invention also relates to a method for determining a desirable humeral stem height.
Various artificial shoulder prostheses with humeral stems are known. Two examples of such prosthesis are shown in U.S. Pat. Nos. 5,728,161 and 5,314,479. The prosthesis of the ""161 patent generally includes a shank portion, a head portion and an attachment mechanism for securing the head portion to the shank portion. Some prosthetic shoulders, such as that shown in FIG. 1 of the ""161 patent, include one or more fins formed on the body portion of the device. The fins may include suture holes. In other prosthetic shoulders, some or all of the fins do not include suture holes. Such a device is shown in FIG. 1 of the ""479 patent. Additional shoulder prosthesis are shown and discussed in U.S. Pat. No. 5,032,132 to Matsen et al.; U.S. Pat. No. 4,865,605 to Dines et al.; U.S. Pat. No. 4,919,670 to Dale et al.; U.S. Pat. No. 5,358,526 to Tornier, U.S. Pat. No. 5,507,817 to Craig et al.; U.S. Pat. No. 4,045,825 to Stroot; and U.S. Pat. No. 4,042,980 to Swanson et al.
Shoulder prostheses are sometimes used to repair what is known as a xe2x80x9cfour part humeral fracture.xe2x80x9d Such a fracture typically occurs in the proximal region of the humerus. Often, the humeral head, greater tubercle and lesser tubercle separate from the humeral shaft, thus leaving four parts. A shoulder prosthesis may be used to replace the humeral head and provide a point of attachment for the greater and lesser tubercles.
One embodiment of the present invention provides a shoulder prosthesis including a body having an exterior surface, a shank connected to the body, a head connected to the body, a medial fin connected to the body, the medial fin including at least one suture hole, a posterior fin connected to the body, the posterior fin including at least one suture hole, an anterior fin connected to the body, the anterior fin including at least one suture hole and at least one lateral suture hole intersecting the exterior surface of the body. The suture hole may be formed in a projection on the exterior surface of the body. At least one of the anterior and posterior fins may extend farther above the exterior surface of the body than the projection. At least one of the anterior and posterior fins may extend at least twice as far above the exterior surface of the body as the projection. A plurality of the suture holes in the anterior and posterior fins and the lateral suture hole may lie in the same plane.
According to another embodiment of the present invention, a shoulder prosthesis includes a body having an exterior surface, a shank connected to the body, a first suture hole located on the lateral side of the prosthesis and an anterior fin connected to the exterior surface of the body, the anterior fin having a second suture hole the center of which is spaced farther from the exterior surface of the body than the center of the first suture hole. The first suture hole may intersect the exterior surface of the body and may be formed in a projection on the exterior surface of the body. In one embodiment, the anterior fin extends farther above the exterior surface of the body than the projection. The anterior fin may extend at least twice as far above the exterior surface of the body as the projection. The shoulder prosthesis may include a posterior fin having a third suture hole the center of which is spaced farther from the exterior surface of the body than the center of the first suture hole. The first, second and third suture holes may lie in the same plane.
According to another embodiment of the present invention, a shoulder prosthesis includes a body having an exterior surface, a shank portion attached to the body, the shank portion configured to be received within the medullary canal of a human humerus, an anterior fin including at least one suture hole, the anterior fin and at least one suture hole providing an attachment point for the greater and lesser tubercles and a least one lateral suture hole intersecting the exterior surface of the body, the at least one lateral suture hole providing an attachment point for the greater tubercle to prevent rotation of the greater tubercle. At least one lateral suture hole may be formed in a projection on the exterior surface of the body. The anterior fin may extend farther above the exterior surface of the body than the projection and may extend at least twice as far above the exterior surface of the body as the projection. The prosthesis may also include a posterior fin including at least one suture hole, the posterior fin and at least one suture hole providing an attachment point for the greater and lesser tubercles. In one embodiment, at least one lateral suture hole lies in the same plane as at least one of the suture holes in the anterior fin and at least one of the suture holes in the posterior fin.
According to an additional embodiment, a trial stem is provided with measurement indicia thereon and a shoulder prosthesis is provided with corresponding indicia thereon.
Also according to the present invention, a method is provided for positioning a shoulder prosthesis so as to allow for ample space for anatomic reconstruction of the tuberosities and anatomic reconstruction of the humeral articular surface. The method includes using a trial prosthesis, noting the position an indicia on the trial and upon implantation of the actual prosthesis, positioning a corresponding indicia in the same location.